Police are investigating how the boy, named Cooper, ended up in the back of 33-year-old Justin Ross Harris' vehicle. Harris, of Marietta, Ga., initially told police he went to work at around 9 a.m. on Wednesday. He said he was supposed to bring the boy to daycare, but instead forgot and went to work.

The boy was strapped in his car seat in the back of the vehicle for seven hours as the temperature rose to 88 degrees.

Around 4 p.m., as he was driving home from work, Harris said that he noticed that his son was in the back seat and pulled over at a shopping center. Harris tried to perform CPR on the boy, according to a witness, but the child was pronounced dead at the scene.

Police filed criminal charges against Harris on Thursday as they investigate the circumstances behind the boy's death.

"Investigators are trying to really nail down...the sequence of events and how that happened," said Sgt. Dana Pierce of the Cobb County Police Department. "We have been in communication with the mother. We will continue that communication as well as our investigation."

Harris, who works for Home Depot, is being held without bond in the Cobb County Jail. A bond hearing was set for July 15.

On the day after Memorial Day, Georgia's governor announced a campaign called "Look Again" to make parents aware of the dangers of heat stroke for children and pets as the weather warms.